Short Description: Removed shared public STL iterator from WorkspaceSelection
Bug Number: n/a
Release notes (y/n): no
For Release Nums: 6.2

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Q3GUI/WorkspaceSelection.hpp
Q3GUI/WorkspaceSelection.cpp
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Removed two virtually-unused shared public STL iterators from the ancient
"WorkspaceSelection" class.  One of these was causing a crash in 6.2
develoment when deleting a single selected data object.  I couldn't 
create the problem in other contexts (including the 6.1 release), so I'm
just removing these iterators without filing a gnats entry.

See stack trace and code snippet (at bottom):
https://cadswes2.colorado.edu/~philw/2012/bugs/crash1/DelMassBalWsObj.html

It's difficult to keep a "persistent" STL iterator valid, in part because 
the NULL value of an iterator depends on the content of the collection.
This crash was happening in some code to implement that maintenance. But 
actually, a shared public STL iterator is a bad idea anyway -- it can be 
used only for one thing at a time, so really the client code should just
create its own.

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